Hydraulic booster control



3 Sheets-Sheet 1 INVENTOR WABI;TER GERSTENBERGER AGE NT w. GERSTENBERGERHYDRAULIC BOGSTER CONTROL Original Filed Sept. 26, 1950 1 25 Oct. .25.,1960 Original Filed Sept. 26, 1950 w. GERSTENBERGER 2,957,527 HYDRAULICBOOSTER CONTROL s Sheets-Sheet 2 I90 INVENTOR WALTER GERSTENBERG ERAGENT Oct. 25, 1960 w. GERSTENBERGER 2,

HYDRAULIC BOOSTER CONTROL Original Filed Sept. 26, 1950 I5 Sheets-Sheet3 INVENTOR WALTER GERST'ENBERGER United States Patent HYDRAULIC BOOSTERCDNTROL Walter 'Gerstenberger, Milford, 'Conn., assignor to UnitedAircraft Corporation, East Hartford, Conn., a corporation of DelawareOriginal application Sept. 26, 1950, Ser. No. 186,744,

now Patent No. 2,755,870, dated July 24, 1956. Di-

vided and this application Mar. 12, '1956, Ser. No. 570,736

'Claims. (Cl. 170-16025) This invention relates to helicopters of thetype in which the rotor blades arepivotally mounted on a hub forflapping and coning movement and for pitch changing movement about theirlongitudinal axes and in which the directional control of the helicopterisobtained by varying the pitch of the blades either collectively orcyclically by movements of a swash plate mechanism. The invention isparticularly concerned with an improved servomotor, or boost mechanism,for moving the swash plate in response to movements of the primarycontrols by the pilot. This application is a division of Patent No.2,755,870.

It is an object of the present invention to provide an improved controlsystem including power operated means arranged to relieve the pilot ofthe dynamic and aerodynamic loads and vibrations originating in therotor blades and to eifect movement of the swash plate to control thehelicopter with a minimum of force applied to the pilots controls. Afurther object of the invention is to provide an improved servo controlmechanism of this type in which the pilot can instantly override theservomotor with his manual controls in the event that the servomechanism for any reason fails in service.

Another object of this invention is to provide a servo control mechanismfor a helicopter having a lost motion device between the servomotor andthe connection of the pilot actuated link to the valve for moving saidservomotor.

An object of this invention is to provide a servomotor mechanism inwhich the movable element of the servo unit is in parallel with themechanical linkage between the stick and the swash plate member.

A still further object of the invention is the provision of meansresponsive to the maintenance of fluid pressure in the servo system fordisabling the servo mechanism automatically in the event of failure offluid pressure in the system.

A further object of the invention is generally to improve helicoptercontrol systems. I

These and other objects and advantages of the invention will becomeapparent in connection with the detailed description of two typicalembodiments of the invention shown in the accompanying drawings.

In these drawings:

Fig. 1 is a side elevation of a helicopter embodying one form of theinvention with a part of the fuselage in the vicinity of the rotor headbroken away;

Fig. 2 is a view showing a modified form of servo mechanism and controllinkage.

Fig. 3 is an enlarged detail or part of the control linkage of Fig. 2including the servomotor mechanism.

Fig. 4 is a still further enlarged view of the connection between theservo mechanism and the swash plate;

Fig. 5 is an elevation partly in section of the modified servomotor andvalve;

Fig. 6 is a section on line 6-6 of Fig. 5 rotated 90.

Fig. 7 is an enlarged view of a part of the mechanism of Fig. 6.

Fig. 8 is a diagrammatic view of the servo mechanism showing theinterconnections of passages in the servomotor.

As herein shown in Fig. 1, the helicopter embodying flapping and coningmovement and also for movement,

about their longitudinal pitch changing axes. The helicopter alsoincludes a tail cone 18 terminating in a pylon 20 on which a tail rotor22 is mounted for rotation about a generally horizontal axis. Thefuselage 10 has a passenger or cargo carrying compartment 24 beneath therotor head and a pilots compartment 26 immediately forward of the rotorhead in which the usual pilots controls are provided. These may includethe usual pivoted pilots cyclic pitch control stick 28 by which fore andaft and lateral tilting of the swash plate is eifected. However, for thesake of clarity the lateral control linkages have been omitted. A usualcollective pitch control stick (not shown) may also be provided.

In the embodiment shown in Figs. 2 through 7 an arrangement of theservomotor mechanism is provided in which the movable element of theservo unit is in parallel with the mechanical linkage between the stickand thej swash plate member. There are three servomotor mechanismsincluded in this embodiment and they are identified as units A, B, andC.

Referring to Fig. 2 it will be noted that dual cyclic pitch controlsticks 2811 are provided as well as dual collective pitch levers 162which are connected through linkage means with bosses 63a on thestationary swash plate member (not shown). This control linkage isdescribed more in detail in US. Patent No. 2,811,212.

Thus fore and aft movement of either stick 28a due to its universalsupport 164 will rotate shaft 166 and the arm 168 carried thereby toreciprocate thrust rods 169, 170 and 172 of unit A. This rod 172 ispivoted at its upper end at 174 to the free end of a lever 176 pivotedto fixed structure of the helicopter at 178. Lever 176 thus impartsreciprocatory movement to thrust link 180 (Figs. 2 and 4) which has alost motion pivotal connection 182 with a pivot pin 184 carried by boss63a on the stationary swash plate member. The lost motion is providedbetween sleeves 183 mounted on pin 184 in the bushings 185 of the pivotholes of link 180, each of which has an inside diameter somewhat largerthan the outside diameter of each sleeve 183.

Lateral movements of sticks 28a are efiected in unison by a tie rod 186.A rod 188 connects rod 186 to a rocking lever 190 and through a thrustrod 192 connects the sticks to a double bell crank 194 which has itsopposite arms connected to thrust rods 196 and 197 which aredifferentially operated upon lateral movements of the sticks. Thereciprocatory movements of rods 196 and 197 are transmitted throughsuitable bell cranks and rods 198 and 200 to rods 172 and rods 180, ofunits B and C respectively, previously described in connection with thefore and aft movements. f

Referring to Fig. 3 it will be noted that the servomotor generallyindicated at 50a include-s a cylinder element 204, which also carries acasing 206 housing the valve 208, and a piston element 210 which ispivotally connected at its lower end at 212 to a member 211 which isfixed to structure of the helicopter. The upper end of the cylinderelement 204 is pivotally connected by pivot pin 184 directly with thestationary swash plate, this connection being eifected by a yoke 214between which the boss 63a on the stationary swash plate is re ceived.As shown in Fig. 4 the pivot pin 184 is mounted Patented Oct. 25, 19 60in the inner race of a ball bearing 216 the outer race of which iscarried by the boss 63a. The valve 208 is pivoted at its upper end to athrust link 218 at 220 and this thrust link is pivoted at its other endto the pivot pin 184 on the same lost motion bushings 185carried bythrust link 180 so that the pilot valve has the same lost motionrelative to the pin 184 as the thrust link.

When the pilot moves either stick 28a fore or aft, this movement isconveyed to servomotor mechanism A through the linkage described aboveto move the swash plate up or down at the point63a. When the pilot moveseither stick 28a to one side or the other, this movement is conveyed toservomotor mechanisms B and C moving them in opposite directions. Thatis, when unit B is moving its connection to the swash plate upwardly,unit C is moving its connection to the swash plate downwardly. Thesevarious movements of the servomotor mechanisms place the swash plate invarious positions to provide for cyclic pitch. When the pilot desirescollective pitch, he moves either of levers 162 which actuatesservomotor mechanisms A, B and C equally.

The servomotor in this form operates with fluid under pressure beingadmitted through inlet 222 to an intermediate annular chamber 224 viapassageway 219, space 223 surrounding traverse passage 244 in plug 248,and passageway 225. Upper and lower lands 226 and 228 admit the fluidunder pressure through passages 230 and 232 to the upper and lower sidesof piston 234, it being understood that when fluid is admitted to oneside of the piston the other side of the piston is vented throughsuitable passages 235, 236, 237 into the fluid exit 238.

Passages 230 and 232 are connected by a by-pass passage 239 which inthis embodiment is controlled by valve means automatically responsive topressure of the fluid in space 223. This valve means includes a piston240 (Fig. 6) which controls passage 239 and is constantly biased by aspring 242 into passage open position. The valve is normally maintainedin passage closed position by fluid under pressure in space 223 which istransmitted through transverse passage 244 and axial passage 246 in ascrew threaded plug member 248 to act on the face of the piston 240 in adirection to compress spring 242. Venting means are provided from theopposite side of the piston through passages 241 and 237.

It can be seen that when fluid under pressure is being admitted to theservomotor mechanism, this pressure acts on piston 240 closing passage239 and therefore preventing passage 230 from being connected to passage232. This in turn prevents one end of the servomotor cylinder from beingconnected to the other end. Now when there is a loss of fluid in thesystem, the pressure in inlet 222 will drop and said drop will betransmitted in turn to the valve means including piston 240. This piston240, with the loss of the fluid pressure, will be biased into a positionwhich will open passage 239 and connect passage 230 to passage 232. Theconnection of these passages in turn connects the one end of theservomotor cylinder to the other end. This connection permits manualactuation of the swash plate since fluid cannot now be trapped in thecylindrical element 204 around the piston 234.

Means is provided to partially compensate for the weight of the manuallyoperative linkage mechanism so as to tend to maintain the pivot pin 184substantially centered in the bushings 185 (Fig. 4). To this end a pairof tension springs 250 are connected between pin 184 and lugs 252 onthrust link 180. The presence of these springs insures that the pilotcan always move the valve 208 to effect movement of any servo mechanismin either direction without having to pick up the weight of the linkageconnecting the stick with the stationary swash plate member.

'It will be noted in Figs. 5, 6 and 7 that there is an automatic by-passvalve piston 240.

It will be evident that as a result of this invention improvedmeans'have been provided for"not"'only'operating the swash plate byhydraulic means to relieve the pilot, but that such means has also beenprovided having the hydraulically operated element thereof directlyconnected to the stationary swash plate member to prevent vibrations andotheraerodynamic forces originating in the rotor blades from'beingtransmitted back to the stick.

It will also be evident that improved means has been provided by whichthe pilot can instantly override the hydraulic servo mechanism in theevent of failure of the latter as well as an improved means forautomatically conditioning the mechanism for manual operation in theevent of such failure.

While one embodiment of the invention has been shown and describedherein, it will be evident that various changes may be made in theconstruction and arrangement of the parts without departing from thescope of the invention.

I claim:

1. In a rotary wing aircraft having blades pivoted for pitch changingmovement about their longitudinal axes, means for controlling the pitchof said blades including rotatable and non-rotatable swash platemembers, a pilot control stick, a control member having one endoperatively connected with said non-rotatable swash plate member and theother end connected to said pilot control stick, servomotor mechanism inparallel with said control member including piston and cylinder elementseach having a free end, a member fixed to aircraft structure, one ofsaid elements having its free end pivoted to said member fixed toaircraft structure and the other element having its free end connectedto said non-rotatable swash plate member, a source of fluid underpressure, a valve for selectively admitting hydraulic fluid from saidsource to opposite sides of said servo piston having a direct operativeconnection to said pilot control stick, a passage connecting oppositesides of said servo piston, and valve means responsive to fluid pressurein said source for controlling the flow of fluid in said passage.

2. In a rotary wing aircraft having blades pivoted for itch changingmovement about their longitudinal axes, means for controlling the pitchof said blades collectively and cyclically including rotatable andnon-rotatable swash plate members, pilot operated control meansincluding a pilot operable member and linkage means connecting saidpilot operable member with said non-rotatable swash plate member, saidlinkage means including an upright link member having a pivotal lostmotion connection to said non-rotatable swash plate member, servomotormechanism including a cooperating servo piston and housing having oneend connected with said non-rotatable swash plate member and having itsother end pivoted to fixed structure of said aircraft, a source of fluidunder pressure, a valve for admitting hydraulic fluid from said sourceto opposite sides of said servo piston, link means connecting said valveto said upright link member whereby initial motion of the latterrelative to said non-rotatable swash plate member operates said valveprior to direct manual operation of said swash plate.

3. In a rotary wing aircraft having blades pivoted for pitch changingmovement about their longitudinal axes, means for controlling the pitchof said blades including rotatable and non-rotatable swash platemembers, a servomotor mechanism including a cooperating servo piston andhousing, first means pivotally connecting one end of said mechanism withsaid non-rotatable swash plate member, means connecting the other end ofsaid mechanism to fixed structure of said aircraft, a source of fluidunder pressure, a pilot operable member, a valve for admitting hydraulicfluid from said source to opposite sides of said servo piston, secondmeans pivotally connecting said valve to said pilot operable member, thepivotal connection of said first means and the pivotal'connection ofsaid second means having a'con1- mon pivotal axis at rest, the pivotalconnection of said first means having a lost motion connection with thepivotal connection of said second means.

4. In a rotary wing aircraft having blades pivoted for pitch changingmovement about their longitudinal axes, means for controlling the pitchof said blades including rotatable and non-rotatable swash platemembers, a servomotor mechanism including a cooperating servo piston andhousing, first means connecting one end of said mechanism with saidnon-rotatable swash plate member, said first means comprising a pinpassing through a portion of both said one end of said mechanism andsaid non-rotatable swash plate member, a member fixed to said aircraft,means connecting the other end of said mechanism to said membercomprising a pin passing through a portion of both said other end ofsaid mechanism and said member fixed to said aircraft, a source of fluidunder pressure, a pilot operable member, a valve for admitting hydraulicfluid from said source to opposite sides of said servo piston, a linkhaving one end connected to said valve, second means connecting theother end of said link to said pilot operable member, said second meanscomprising bushing means passing through a portion of both said link andsaid pilot operable means, said pin and said bushing means having acommon axis when at rest, said bushing means surrounding said pin andhaving a larger inner diameter than the outer diameter of the pinproviding a lost motion connection.

5. In a rotary wing aircraft having blades pivoted for pitch changingmovement about their longitudinal axes, means for controlling the pitchof said blades including rotatable and non-rotatable swash platemembers, a servomotor mechanism including a cooperating servo piston andhousing, first means connecting one one, of said mechanism with saidnon-rotatable swash plate member, said first means comprising a pinpassing through a portion of both said one end of said mechanism andsaid non-rotatable swash plate member, means connecting the other end ofsaid mechanism to fixed structure of said aircraft, a source of fluidunder pressure, a pilot operable member, a valve for admitting hydraulicfluid from said source to opposite sides of said servo piston, a linkhaving one end connected to said valve, second means connecting theother end of said link to said pilot opera'ble member, said second meanscomprising bushing means passing through a portion of both said link andsaid pilot operable means, said pin and said bushing means having acommon axis at rest, said bushing means surrounding said pin and havinga larger inner diameter than the outer diameter of the pin providing alost motion connection, and resilient means connected between said pilotoperable member and said non-rotatable swash plate member to locate saidbushing means around said pin.

References Cited in the file of this patent UNITED STATES PATENTS Re.22,728 Burton et a1. Mar. 5, 1946 2,179,179 Fischel et a1. Nov. 7, 19392,337,706 Berry Dec. 28, 1943 2,405,188 Campbell Aug. 6, 1946 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 2,957,527October 25 1960 I. Walter Ger'e tenberger It is hereby certified thaterror appears in the printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

' Column 6, line S -for- Fone" read end Signed and sealed this 11th dayof April 1961,

(SEAL) Attest:

I ARTHUR W1CROCKER g gmg SWIDER r A ti Commissioner of Patents

